X-Y carriage moving systems are widely used in robot arms for moving a work from one location to another, in X-Y plotters for moving a pen along a prescribed path to draw various drawings on a sheet of paper or the like, and in cutting tools for moving a cutting tool along a prescribed path to cut out a plate or sheet member into a desired shape. In such a system, typically, the working end, such as a robot finger, a pen and a cutting tool, is carried by a carriage guided by a Y-axis guide and driven in the Y-direction by a Y-axis drive motor. The Y-axis guide and the Y-axis drive motor are carded by a Y-axis unit which is in turn supported by a X-axis guide and driven in the X-direction by a X-axis drive motor. By appropriately actuating the X- and Y-axis drive motors, it is possible to move the working end to a desired location in a X-Y coordinate system. However, according to a typical conventional system, the Y-axis unit travels along the X-axis guide, and the relatively large mass or the inertia of the Y-axis drive motor incorporated in the Y-axis unit and the presence of power cables for the Y-axis drive motor have been known to be major problems. The relatively large mass of the Y-axis unit correspondingly requires a relatively rigid guide structure, and it is detrimental to the reduction in the cost and the size of the system. More importantly, the inertia of the Y-axis unit is highly disadvantageous in increasing the response speed of the working end. Also, the presence of the power cables is a problem because it requires some arrangement to keep the power cables from interfering with the movement of the system, and the cables adds to the mass of the Y-axis unit.